Build, test, and debug regular expressions
Matches lines containing a price that starts with a dollar sign and ends in '.99' (e.g., '$19.99'), capturing the full price in a named group 'sale_items'. The positive lookbehind (?<=\.99) combined with the $ anchor ensures the matched price ends with 99 cents, a common sales pricing convention. With multiline mode enabled, it processes each line individually, making it ideal for extracting sale prices from product listings, receipts, or pricing files.